Untangling the myths about HEAD LICE.

Head lice: The idea alone is enough to make your scalp itch. Each year, there are 6 million to 12 million lice cases in U.S. children ages 3 to 11, according to the Centers for Disease Control and Prevention. It’s a year-round scourge, though the number of cases seems to peak when kids go back to school in the fall and again in January, possibly due to familial mingling during the holidays.

There are almost as many misconceptions about the parasites as there are critters. M.J. Eckert, a former school nurse and co-founder of Lice Happens, an Annapolis-based in-home lice treatment and removal service, says she once met a father who’d used a high-powered shop vacuum on his son’s infested head, hoping to suck the problem away. Another family threw out a sleeper sofa in the middle of the night, convinced that it was the source of an intractable lice infestation.

Neither approach worked.

First, some facts: The head louse is a six-legged wingless insect known as an ectoparasite, meaning that it makes its home on a host’s surface. It’s related to the body louse, which, unlike the head louse, can carry disease. The animal needs blood and a warm environment to survive. That’s why it finds such comfort in the human scalp; it also likes to root itself in the nape of the neck and behind the ears.

Once it has set up shop, the insect lays pinhead-size tan or whitish-colored eggs, known as nits. The mother louse excretes a kind of glue to cement the nits to the hair shaft, close to the scalp so its warmth can incubate them. They hatch about a week later into baby lice, called nymphs. In a typical infestation, there are more nits than bugs since an adult louse will lay an average of five to 10 eggs a day and a newborn female needs only 10 days to become a mom. So the family tree grows quickly.

Head lice are undeniably gross. Eckert says she faces tears and panic from parents every day. “Seeing [lice] in their kid’s hair,” Eckert says, “makes a normally sane person insane.”

The American Association of Pediatricssuggests that kids with lice stay in school: “Because a child with an active head lice infestation likely has had the infestation for 1 month or more by the time it is discovered and poses little risk to others from the infestation,” its guidelines say, “he or she should remain in class but be discouraged from close direct head contact with others.”

Some public school systems in the Washington area follow that let’s-not-panic approach, including those in Arlington and Fairfax counties. Both ask that students be treated for live lice before they return to school, but children are allowed back with nits. The written policy in Montgomery County and the District, however, says students are to be kept home until they are free of both lice and nits.

It doesn’t help that there’s such confusion about how the little beasts operate. Here are a few common myths:

1. You’re more likely to get lice if you’re dirty

“Head lice has nothing to do with hygiene,” says Andrew Bonwit, a pediatric infectious-disease expert at Loyola University Health System outside Chicago. “It has to do with whether the person was exposed to someone with head lice.” Bonwit says a louse, which is “about the length of George Washington’s nose on a quarter,” doesn’t have discriminating tastes: It wants warmth for its eggs and a regular “blood meal.” It doesn’t matter if the dish is dirty or clean.

2. Your pet can carry lice

Lice feed only on humans. Fleas and ticks are another story.

3. Lice can jump and fly

No. They just crawl. That’s why kids are so much more likely than adults to have lice: They often touch heads when interacting, whether playing or talking or sleeping together at slumber parties (which are top-notch settings for lice transmission). A few lice can quickly scuttle over hair to a new head while, say, kids press close to take photos, snuggle up to watch a movie or share a pillow. While adults can get lice from their children, they rarely are the family members to bring the bugs home. (As Bonwit points out, “In the typical office, there’s probably not a whole lot of hugging going on.”)

4. Your house can get infested with lice

While scientists agree that lice almost always spread by crawling from head to head, they’re less sure how often they travel from head to pillow to head. The bugs “probably don’t voluntarily leave a scalp,” says Dale Clayton, a lice expert and biology professor at the University of Utah in Salt Lake City.

“Because if you think about it, that’s dangerous for them. But they may get brushed off from time to time.”

Eckert says she tries to reassure clients that “Lice are very good at holding on to hair. And they are not microscopic. You’re going to see them if they’re on a pillow.”

She also says there’s no need to wash everything in a home where lice have been spotted; she’ll tell people to wash their bedding not because there are bugs in the bed (there probably aren’t — and if there are, they’re dying) but because lice leave droppings, which look like tiny dark specks. “You don’t want to be sleeping on lice excrement,” she says.

5. You need special over-the-counter shampoos to get rid of the lice and nits

Shampoos such as Nix and Rid kill live lice — but not always and not all of them. Many lice have developed resistance to the most common active ingredients, permethrin and pyrethrins. And they don’t kill all of the nits.

In fact, use of these products has led to super lice, bugs that are developing a resistance to some insecticides. Already this year, at least one U.S. school district has reported an uptick in cases of super lice. “Evolutionary resistance has gotten much worse in the past 10 or 20 years,” Clayton says. When he grew up in Great Falls in the 1960s, he says, “I never heard of anybody who had lice. Now they’re very, very common.”

But Eckert says that, pesticide resistance or no, the key is “meticulous combing” with a fine-toothed metal comb that removes the eggs from the hair shaft.

“It’s time-consuming, back-breaking work,” says Kay Sessoms, whose two daughters, 11 and 13, have had “the four-letter L-word” at least four times each over the past seven years. Sessoms, who lives in Bethesda, adds that she has spent the length of “two Disney movies” combing out the nits from each daughter’s hair, inch by inch.

Eckert and Lice Happens’s 12 other “lice specialists” can do a full comb-out in an average of 90 minutes for girls and as little as 15 or 20 minutes for boys (the price is $100 an hour plus a service-call fee), and they will teach parents how to do the necessary follow-up combing for the next 14 days.

6. You can suffocate lice

Eckert says she’ll show up for house calls and parents will come to the door with their child’s hair covered in petroleum jelly, wrapped in cellophane and topped with a shower cap. “They read online somewhere that you can suffocate lice with Vaseline, olive oil or mayonnaise,” she says. “They get dubious results at best, and it’s not going to kill the nits.”

7. If you have lice, your head will be itchy

Many people with lice don’t itch. For those who do, the itchiness may not begin until a few weeks into the infestation. Since head scratching isn’t always present as a warning sign, many experts suggest that parents do periodic lice checks on their children.